Analog Telephone Network
Analog telephony, popularly known as “Plain Old Telephone Service” (“POTS”) has been in existence for over 100 years, and is well-designed and well-engineered for the transmission and switching of voice signals in the 3-4 KHz portion (or “band”) of the audio spectrum. The familiar POTS network supports real-time, low-latency, high-reliability, moderate-fidelity voice telephony, and is capable of establishing a session between two end-points, each using an analog telephone set.
The terms “computer” and “personal computer” (“PC”) as used herein include workstations and other data terminal equipment (DTE) with interfaces for connection to a local area network. The term “telephone set” as used herein includes any device which can connect to a Public Switch Telephone Network (“PSTN”) using analog telephone signals, non-limiting examples of which are fax machines, automatic telephone answering machines, and dial-up modems.
Outlets
The term “outlet” herein denotes an electromechanical device, which enables connection to wiring installed within a building. Outlets are permanently connected to the willing, and allow easy connection of external units as required to such wiring, commonly by means of an integrated, built-in connector. The outlet is normally mechanically attached to, or mounted in, the wall. Non-limiting examples of common outlets include: telephone outlets for connecting telephone sets; CATV outlets for connecting television sets, VCR's, and the like; and electrical outlets for connecting power to electrical appliances.
LAN Environment
A development associated with the Internet is packet telephony. Packet telephony involves the use of a packet based network (commonly using the Internet Protocol, or IP) for communicating telephonic and related data, which may include sound, images, motion pictures, multimedia and any combinations thereof, in addition to voice content. In place of a pair of telephones connected by switched telephone lines as in analog telephony, packet telephony typically involves the use of an IP-telephone at one or both ends of the telephony link, with the telephonic information transferred over a packet network using packet switching and packet routing techniques, as exemplified by the Internet.
Recently, a solution for combining both telephony and data communications into a single network is offered by the Voice-Over-Internet-Protocol (VoIP) approach. In this technique, telephone signals are digitized and carried as data across the LAN. Such systems are known in the art.
FIG. 1 shows a typical LAN-based telephony environment 10. Such a network, commonly using 10BaseT or 100BaseTX Ethernet IEEE802.3 interfaces and topology uses a hub 11 as a concentrating device, into which all devices are connected. Devices are connected to hub 11 by data connectors 14a, 14b, and 14c, which are housed within network outlets 15a, 15b, and 15c respectively via cables 13a, 13b, and 13c respectively. Data connectors 14a, 14b, and 14c may be, for example, type RJ-45; and cables 13a, 13b, and 13c may be, for example, Category 5 cabling. The telephony portion of network 10 uses IP telephones 17a, 17b, and 17c, which connect to network connectors 14a, 14b, and 14c via cables 16a, 16b, and 16c, respectively. A server 12 may also be connected to hub 11, and can perform the IP-PBX functionality, as well as other server functions as applied in the art.
Although FIG. 1 refers to the hub 11 as a concentrating device, it is understood that any type of device having multiple network interfaces and supporting a suitable connectivity can be used, non-limiting examples of which include a shared hub, switch (switched hub), router, and gateway. Hence, the term “hub” used herein denotes any such device. Furthermore, the hub 11 can be any packet based network, either in-building or distributed, such as LAN or the Internet.
In order to employ VoIP in network 10, specific IP telephones 17a, 17b, and 17c must be used. Such telephones are expensive, require connection to a power outlet (or other power supply) and are not yet common in the marketplace. This factor has encouraged the availability of adapters for bridging between IP networks and PSTN equipment. Specifically, adapters enabling the usage of POTS telephone sets in an IP environment are available in the market, allowing the use of common and low-price legacy POTS telephone sets to be used in a VoIP environment.
FIG. 2 shows a network 20 using POTS telephone sets in a VoIP environment. Basically, network 20 uses the same network infrastructure as network 10 (FIG. 1) . However, instead of IP telephones 17a, 17b, and 17c, POTS telephone sets 22a, 22b, and 22c are used, connected via cables 6a, 6b and 6c respectively to VoIP / PSTN adapters 21a, 21b, and 21c, respectively, which in turn are respectively connected to network outlets 15a, 15b, and 15c via cables 23a, 23b and 23c respectively. Such a configuration affords the benefits of IP telephony, but allows the use of common and inexpensive POTS telephone sets.
Although network 20 facilitates the employment of common, low-cost standard legacy POTS telephone sets, adapters 21a, 21b, and 21c are necessary, making installation and maintenance complex, and requiring additional equipment, connections, and cables (e.g. cables 23) . Furthermore, such adapters require a power connection, further complicating installation, use, and maintenance.
Furthermore, although FIG. 1 and FIG. 2 show networks which are used solely for telephony, LANs today are intended and used principally for data communication, to connect Data Terminal Equipment (DTE) devices (such as desktop personal computers, printers). In some cases, the number of outlets 15 (or connectors 14) may not suffice for both telephony and data applications. For example, this may be the case in an office where each work area has a single network connection via a single outlet 15 having single connector 14. In this case, a hub (or other multi-port unit) must be connected to expand to multiple network connections. FIG. 3 shows such a configuration in a prior-art network 30. In order to allow both adapter 21a and DTE 7a to share network outlet 15a via connector 14a, a hub 31a is added. Similarly, a hub 31c is added, facilitating the connection of both adapter 21c and DTE 7c to a single network connection via outlet 15c via connector 14c. Thus, in such a configuration, additional hubs 31a and 31c must be added, introducing additional complexity in installation and maintenance.
Home Networking
In-home telephone service usually employs two or four wires, to which telephone sets are connected via telephone outlets.
FIG. 4 shows the wiring configuration of a prior-art telephone system including a network 40 for a residence or other building, wired with a telephone line 5. The telephone line 5 consists of single wire pair which connects to a junction-box 34, which in turn connects to a Public Switched Telephone Network (PSTN) 410 via a cable 33, terminating in a public switch 32, which establishes and enables telephony from one telephone to another. The term “analog telephony” herein denotes traditional analog lowfrequency audio voice signals typically under 3 KHz, sometimes referred to as “POTS” (“Plain Old Telephone Service”) , whereas the term “telephony” in general denotes any kind of telephone service, including digital service such as Integrated Services Digital Network (ISDN). The term “high-frequency” herein denotes any frequency substantially above such analog telephony audio frequencies, such as that used for data. TSDN typically uses frequencies not exceeding 100 KHz (typically the energy is concentrated around 40 KHz) . The term “telephone line” herein denotes electrically-conducting lines which are intended primarily for the carrying and distribution of analog telephony, and includes, but is not limited to, such electrically-conducting lines which may be pre-existing within a building and which may currently provide analog telephony service. The term “telephone device” herein denotes, without limitation, any apparatus for telephony (including both analog telephony and ISDN), as well as any device using telephony signals, such as fax, voice-modem, and so forth.
The junction box 34 is used to separate the in-home circuitry from the PSTN and is used as a test facility for troubleshooting as well as for new wiring in the home. A plurality of telephones may connect to telephone lines 5 via a plurality of telephone outlets 35a, 35b, 35c, and 35d. Each outlet has a connector (often referred to as a “jack”), denoted in FIG. 4 as 36a, 36b, 36c, and 36d, respectively. In North-America, RJ-11 is commonly used for a jack. Each outlet may be connected to a telephone unit via a “plug” connector that inserts into the jack.
Network 40 is normally configured into a serial or “daisy-chained” topology, wherein the wiring is connected from one outlet to the next in a linear manner, but other topologies such as star, tree, or any arbitrary topology may also be used. Regardless of the topology, however, the telephone wiring system within a residence always uses wired media: two or four copper wires along with one or more outlets which provide direct access to these wires for connecting to telephone sets.
It is often desirable to simultaneously use existing telephone wiring simultaneously for both telephony and data networking. In this way, establishing a new local area network in a home or other building is simplified, because there is no need to install additional wiring. U.S. Pat. No. 4,766,402 to Crane (hereinafter referred to as “Crane”) teaches a Local Area Network over standard two-wire telephone lines, but does not simultaneously support telephony.
As another example, relevant prior-art in this field is disclosed in U.S. Pat. No. 5,896,443 to Dichter (hereinafter referred to as “Dichter”). Dichter suggests a method and apparatus for applying a frequency domain/division multiplexing (FDM) technique for residential telephone wiring, enabling the simultaneous carrying of telephony and data communication signals. The available bandwidth over the wiring is split into a low-frequency band capable of carrying an analog telephony signal, and a high-frequency band capable of carrying data communication signals. In such a mechanism, telephony is not affected, while a data communication capability is provided over existing telephone wiring within a home.
The concept of frequency domain/division multiplexing (FDM) is well-known in the art, and provides means of splitting the bandwidth carried by a wire into a low-frequency band capable of carrying an analog telephony signal and a high-frequency band capable of carrying data communication or other signals. Such a mechanism is described, for example, in U.S. Pat. No. 4,785,448 to Reichert et al. (hereinafter referred to as “Reichert”). Also widely used are xDSL systems, primarily Asymmetric Digital Subscriber Loop (ADSL) systems.
In addition to illustrating a residential telephone system, FIG. 4 also shows the arrangement of a Dichter network. Network 40 serves both analog telephones and provides a local area network of data units. Data Terminal Equipment (DTE) units 7a, 7b, and 7c are connected to the local area network via Data Communication Equipment (DCE) units 39a, 39b, and 39c, respectively. Examples of Data Communication Equipment include, but are not limited to, modems, line drivers, line receivers, and transceivers (the term “transceiver” herein denotes a combined transmitter and receiver), which enables S communication over telephone line 5. DCE units 39a, 39b, and 39c are respectively connected to high pass filters (HPF) 38a, 38b, and 38c, which allow access to the high-frequency band carried by telephone line 5. In order to avoid interference to the data network caused by the telephones, low pass filters (LPF's) 37a, 37b, and 37c are added to isolate the POTS carrying band, so that telephones 22a, 22b, and 22c connects to telephone line 5 for providing PSTN. Furthermore, a low pass filter may also connected to Junction Box 34 (not shown in the figure), in order to filter noise induced from or to PSTN wiring 33.
FIG. 5 shows a telephone line-based LAN 50 wherein the data network is used for carrying both VoIP telephony and regular DTE network data. Hubs 31a, 31b, and 31c allow connecting respective DTE units 7a, 7b, and 7c as well as respective IP telephones 17a, 17b, and 17c to respective single network connections via DCE units 39a, 39b, and 39c. Analog telephones 22a, 22b, and 22c are also shown connected via respective low pass filters (LPF's) 37a, 37b, and 37c to the telephone outlets 35a, 35c, 35d. Thus, the analog telephones are connected directly to the analog telephone line 5.
In order to eliminate the need for IP telephones 17a, 17b, and 17c, and to permit using analog telephone sets 22a, 22b, and 22c instead, adapters 21a, 21b, and 21c (FIG. 3) must be added, as described previously. FIG. 6 shows a network 60, where this is done. IP telephones 17a, 17b, and 17c of network 50 are replaced by analog telephone sets 22d, 22e, and 22f, respectively, connected to hubs 41a, 41b, and 41c, respectively, via adapters 21a, 21b, and 21c respectively.
FIG. 6 demonstrates the complexity of such a configuration. At least three types of external devices are required: DCE units 39a, 39b, and 39c; hubs 41a, 41b, and 41c; and adapters 21a, 21b, and 21c. Each of these devices usually requires a separate power connection, which adds to the complexity of the connections. Thus, such a network is complex and difficult to install, operate, and maintain. In the prior art, it is suggested to integrate the DCE, HPF, and LPF components into outlets 35a, 35b, and 35c. Nevertheless, external hubs 41a, 41b, and 41c, as well as adapters 21a, 21b, and 21c still impose additional complexity in such a network.
There is thus a widely recognized need for, and it would be highly advantageous to have, a means for allowing the use of analog (POTS) telephone sets in LAN/VoIP environments without requiring additional external devices and allowing easy installation, operation, and maintenance. This goal is met by the present invention.